My earnest opinion : China numbers are accurate until proven otherwise.
To be honest I don't care much for the constant comments everywhere about they're covering up the numbers, man ! Not just China, but Iran, Japan and every other country. It's not healthy skepticism most of the time IMHO.
Still, governments lie. Authoritarian regimes lie. Marxist Leninist Popular Democracies lie. Massive health crisis are minimised all the time, even if it's more incompetence than malice. And even with some sympathy for China, I certainly believe they have better control over the means to do so than liberal countries.